Inflammatory cytokine production in interferon-gamma-primed mice, challenged with lipopolysaccharide. Inhibition by SK&F 86002 and interleukin-1 beta-converting enzyme inhibitor

Mice challenged with lipopolysaccharide (LPS) produce variable serum levels of pro-inflammatory cytokines, and particularly low levels of interleukin- 1 beta (IL-1 beta). Interferon-gamma (IFN-gamma) has been shown to be an im portant mediator of bacteria-induced hypersensitivity to LPS in mice. In th e present study, we show that mice pretreated with IFN-gamma exhibit an enh anced capacity to produce serum LL-1 beta, IL-1 alpha, tumour necrosis fact or (TNF-alpha) as well as IL-6 in response to LPS. Priming with intraperito neal (i.p.) injection of 15 mug rat recombinant IFN-gamma, 18 hours prior t o the i.p. LPS (300 mug) challenge resulted in a 4-fold increase in the LPS -stimulated release of IL-1 beta and a 2- to 7-fold increase in the release of IL-1 alpha, TNF-alpha, as well as IL-6 into the serum. LPS induced a co ncentration-dependent increase in the release of IL-1 beta in isolated peri toneal macrophages from IFN-gamma -primed mice whereas macrophages from unp rimed mice released minute amounts of IL-1 beta. In addition, nigericin mar kedly enhanced the release of IL-1 beta in unprimed mice but not in macroph ages from IFN-gamma primed mice. The cytokine synthesis inhibitor SK&F 8600 2, administered per os (100 mg/kg), 1 hour prior to LPS challenge, strongly inhibited the rise in serum levels of the four cytokines. Furthermore, tre atment with the IL-1 beta converting enzyme (ICE) specific reversible inhib itor YVAD-CHO resulted in a sharp dose- and time-dependent inhibition of IL -1 beta secretion in the serum, whereas the other cytokines were not affect ed. In conclusion, IFN-gamma priming strongly potentiates the release of pr oinflammatory cytokines in the serum of mice as compared to LPS stimulation alone, and provides therefore a useful way to test the in vivo potency and selectivity of cytokine synthesis inhibitors.